The overall objective of this research is a better understanding of the mechanisms involved in intestinal calcium transport in physiological, altered physiological and disease states. In order to accomplish this objective, experiments will be undertaken in animals, as well as in humans. In particular, animal experiments are directed towards determining the role of intestinal calcium binding protein, brush border alkaline phosphatase and a basal/lateral membrane adenosine triphosphatase, as they relate to vitamin D metabolism, hormonal relationships and intracellular calcium transport. Experiments in humans will include determination of calcium absorption and endogenous fecal calcium loss, in conjunction with in vitro measures of transport and enzyme activity, using perorally obtained duodenal biopsies from patients with digestive disease disorders. BIBLIOGRAPHIC REFERENCES: Krawitt, E.L., Beeken, W.L. Limitations of Usefulness of the D-xylose Absorption Test. Am. J. Clin. Pathol. 63:261-263, 1975. Krawitt, E.L. Effect of Ethanol Ingestion on Duodenal Calcium Transport. J. Lab. Clin. Med. 85:665-671, 1975.